This depends on the content and the context. Extreme gore descriptions. sexual assault, and anything that is typically seen as torture porn would be a no. That said, there is nothing that prohibits blood, subdued and careful gore. Think Stephen King.
An author that requires a description of every bloody detail is a shit writer, and should pick up a decent horror novel and pay attention. Most of the grim dark stuff this fandom makes is honestly some of the worst text ever put t